Dry kiln



H. W. KhNT.

DRY KILN.

APPLICATION FILED 0012. I92`0.

1,403,417, Patented Jan. 10,1922,

3 SHLE fS-SHEET I.

El El EIEI'EI R. W. KENT.

DRY KILNl APPLICATION FILED OCT, 2, l92 0.

Patented Jan. 10, 1922.

3 sHhETs-sHEl-:T'Ll

.Mw .NTTNT .D n E D D U D D E D D .D D u Se SS TST SP `Nm\ R. W. KENT.

DRY KILN. V APPLICATION FILED OCI-2. |920. 1,403,417., Patented Jan. 10, 1922.;-

3 SHEETSSHEET 3.

' tion of the outer surface of the lumber.

UNITED STATES PATENT OFFICE;

ROBERT W. KENT, OF NEWTON CENTER, MASSACHUSETTS, ASSIGNOR T0 COOLEY &

MARVIN COMPANY, 0F BOSTON,VMASSACHUSETTS', A CORPORATION OF MASSA- cntrsnrrs.

DRY xrLN.

Application led October 2, 1920. Serial No. 414,291.

To all whom 15mg concern:

Be it known that I, RoBnR'r W; KENT, a citizen of the United States of America, and resident of Newton Center, in the county of Middlesex and State of Massachusetts, have invented new and useful Improvements in Dry Kilns, of which thefollowing is a specification.

This invention relates to apparatus yfor articially drying organic material and more particularly to kilns of the continuously acting type adapted for the drying of lumber or the like. V

In such kilns as ordinarily constructed, and in which the lumber is subjected to the action of highly heated air it' is found that the loss of moisture in the lumber is very much less fora, given period of exposure to such heated air than might be expected. This slowness indrying may in many cases be attributed, in part at least, to the condit is found by examination that the surface of air seasoned lumber is much more dense than the interior thereof, due to some extent possibly to the drying thereon of exuded sap and partly to the natural changes in mois- `ture conditions in the atmos herecausing excessive shrlnkage and har ening of the exterior fibers of the lumber, producing thereby a surface hardness commonly known to the trade as case hardening. v

An object of the present invention is to overcome the above mentioned difficulty in the drying of such lumber'by first subjecting the lumber to a process whereby the effects of case hardening are largely neutralized prior to the application thereto of the drying agencies. To this end the drying apparatus may be provided with means for subjecting the lumber to be dried to a prior treatment with moist air or steam, preferably the latter and at such a temperature as to cause softening of the surface of the lumber whereby to permit the dry air, to which the lumber is thereafter subjected, readily to penetrate 'the pores ofthe lumber and to thoroughly dry the same. l

It is found by experiment,.that even with the preliminary steam treatment above described the continuous application of dry heat to the lumber thereafter produces in some cases a secondary case hardening effect somewhat similar to that above described, and a further object of the present invention isto provide in a continuously acting dry kiln, means whereby the. hygroscopic conditions of the air circulating therethrough may be regulated to any desired degree, whereby the most advantageous conditions of the drying medium relativeto heat and moisture may be secured at will. To this end it is proposed to provide the kiln with steam or water sprays distributed at desired points in its length and to provide for the manual and independent control of said sprays.

In kilns of this type it is found difficult to properly control the circulation of air therethrough whereby to bring such air into intimate contact with the heating elementsand thereafter with the lumber to be treated and it is furthermore desirable to employ the same air as the circulating medium throughout the entire length of the kiln, thus avoiding loss'of heat. In practice however, it is foundthat air, after being brought into contact with a certain quantity of lumber becomes so saturated with moisture that it fails to take any further moisture from lumber with which it may thereafter come in contact. A further object of the invention is to provide an arrangement of air conducting flues such that the air may be caused to travel in. a substantially spiral or helical path from one end of the kiln chamber to the other, passing successively through heating coils and over lumber to be treated, then over condensing coils which act to remove part of the absorbed moisture and then again over the heating coils and lumber, etc.

To this end the kiln may be provided with a longitudinally extending chamber having series of air ducts opening at spaced intervals near the bottom lthereof and throughout the length of the same, and a series of outlet flues having their vopenings located in the intervals between the inlet ducts and near the upper portions of the kiln. Within such outlet iues or in continuations thereof, may be arranged condenser coils for removing excess moisture from the air passing throughl said flues, from which point the air may be suitably conducted to the air inlet' duct next in succession in the general direction of air flow through the kiln. If desired, by-pass-channels may be provided to permit the incoming air to be shunted past certain portions of the kiln as for instance, when such portions are not in use.

. line such as G-H of Fig. 3 and In drying type in which the lumber is moved from one end thereof to the other while subjected to lthe action of heat, it is common to have the heating coils run longitudinally of the kiln, but such an arrangement fails to provide for the ready control of heat throughout, the length of the kiln.

A further object of the present invention is to furnish heating means so arranged that the heat at any point in the kiln may be very closely regulated. To this end the heating coils may be arranged in independent units extending transverselyfof the kiln `chamber said units being independently controlledv from a suitable operating station.- Such units are preferably locatedrover the air inlet ducts whereby the air entering through the latter is caused to come in contact with the heating coils and thereby warmed before it rises into contact with the lumber contained in the kiln chamber directly above. If desired the individual heating coils may be of gradually increasing capacity from that end of the kiln at which the lumber is entered toward the end of the kiln from which the lumber is discharged and preferb ably the temperature at the discharge end of the kiln will be maintained much higher than that at the entrance thereof.

As a preferred arrangement for carrying into effect the above objects of the invention the apparatus disclosed in the accompanying drawings has been devised, in Which,-

Fig. 1 is a partial plan view on line A--B of Fig. 4;

Fig. 2 is a fragmentary plan view,the upper portion of said figure being taken on the line B--C of Fig. 4, and the lower portion on the line DI-`E thereof, parts being omitted for the sake of clearness of illustration.

Fig. 3 is a longitudinal cross section with the central portion of the device broken out, such view being taken substantially on the center line of one of the compartments of the device;

Fig. 4 is a transverse cross section on a Fi'g. 5 is a transverse cross sectional view illustrating a suitable arrangement of the controlling station. f

Referring to Figs. 1 and 2 it may be noted that the apparatus constructed in accordance with the present invention will preferably comprise a series of like com artments arranged side by side and in whlch the drying process may be carried out simultaneously.

or convenience of illustration and description, adjacent compartments have been shown as provided only lwith the apparatus lying at selected levels therein, such apparatus being common to all the compartments, however.

The above referred to compartments will ilns of the continuous acting preferably comprise side walls 1 2, a oor 3, and a roof 4, such compartments extending from one end to the other of the apparatus and being normally open at their ends as at 5-f6. Along the floor 3 of the compartments are arranged supports 7 which may be carried upon foundation blocks 8 if desired, such supports being spaced longitudinally of the compartments and in a plurality of series as clearly indicated in'Figs. 1 and 2. Carried upon the supports 7 are uprights 9 upon which are mounted trans- .Versefra'me members 10 such frame members having mounted thereupon longitudinally extending rails 11 of which three are shown in the accompanying drawings. The rails 11 serve to movably support` a truck or trucks indicated diagrammatically at 12 in inl Fig., 4. Upon such trucks may be piled the lumber to be dried and which may thus be moved thereon from one end of the compartment to the other. I

Referring to Fig. 3, 14 is a loading platform adjacent the entrance 5 of the compartment and at 15 is indicated a platform carrying rails 16 along which a car of lumer may be traversed for unloading upon the trucks carried upon the tracks 11., At the opposite end 6 of the compartment is an unloading platform 17 at which point the lumber from the trucks may be deposited upon a suitable car carried upon tracks 18 running along the platform 19. Above said platform 19 may be supported a roof 20 for the protection of the treated lumber during transfer.

As clearly indicated in Fig. 2 the lateral walls 1 and 2 of the compartments, which may be of masonry if desired, are provided with a series of vertical flues 21, such flues being spaced longitudinally of the compartment and opening into the` compartment near its roof as indicated at 22 (see Fig, 4).

25 and 26 are a pairof air ducts (see F ig. 1) extending longitudinally of the compartment, suchl ducts being provided with series of outlet openings 27, 28, spaced apart longitudinally of the ducts. Leading from the lower ends of the respective flues 21 are air passages 29 connecting with the ducts 25, 26 at points in the sides thereof immediately adjacent to the corresponding openings 27, 28, therein. As will be clear from inspection of Fig. 1, each opening 27 of a longitudinal series is arranged substantially opposite the center of the laterally adjacent flue 21, the

passage'29 for conducting air to each of said openings leading from thenext adjacent flue Athrough which air may be admitted either under pressure from a suitable blowing system or under the influence of the natural draft created by the heating of the air within the compartment. The air inlet openings 27, 28, 30, 31 are all located very closely adjacent the floor of the compartment and above Such inlet openings are arranged a series of transversely extending heating coils 32, 33 (Fig. 2). The coils 32' comprise two vertical tiers of pipes, while the. coils 33 comprise a single tier of pipes. As illustrated in Fig. 2 the capacity of the coils gradually diminishes from the discharge end 6 of the compartment toward the intake end 5 thereof. These heating coils are arranged to be fed with steam through header pipes 34, 35, and are individually controlled by means of independent valves 36. By this arrangement it is possible to control the amount of heat admitted to any portion of the compartment, and by arranging the coils so that those of largest capacity are adjacent the discharge end, it is possible to maintain a higher temperature at such end of the compartment than at the entrance thereof.

Located above the heating coils at desired points and as indicated at 37, 38, Fig. 2, may be arranged a series of spray heads through which hot and moist steam may be discharged into the compartment. Preferably one of such series of spray heads as 37 will be arranged in the portion of the compartment closely adjacent the entrance 5 and if desired the heating coils and air ducts may be omitted from this portion of the compartment. Preferably, too, this end of the compartment may be separated from the remainder thereof by means of a curtain' 39 or other suitable and readily removable closure means. The group of spray heads 38, is as above stated, arranged above the level of the heating c'oils and' such spray heads may be placed at any desired points longitudinally of the chamber, it being understood that several independent groups of such spray heads may beA employed if desired. The discharge steam through the spray heads may be controlled by means of independent valves 40 located in the controlling compartment as seen in Fig. 5.

Immediately inside the curtain 39in the direction of travel of lumber through the compartment may be arranged a cupola 41 formingl a discharge passage for the air circulating through the compartment.

Near the lower portion of eachof the tiues 21 is arranged a vertical coil of pipes 42 through which cold water or other refrigerating medium maybe circulated. The circulation of water through such coils may be independently controlled as by means of valves in thecontrolling compartment or -at other suitable points.

lVithin the air ducts 25,-26 are a series of dampers 44, 45, such dampers being arranged between adjacent openings 27, 28 respectively, and serving when in closed position to compel the air traveling through the ducts 25, 26, to pass out through the opening 27 next in advance of the closed damper but when such dampers are allowed to remainopen a large portion of the air traversing the ducts 25, 26, Will move on' ward through the ducts until arrested by a damper when it will discharge through the opening next preceding the damper. By this arrangement it is possible to shunt the air by one or more of the discharge openings 27.

In the operation of the device the lumber received from the Source of supply will be loaded upon a truck 12 standing from the platform 14 and the loaded truck will then be moved along the rails 11 into the portion X of the compartment immediately in advance of the curtain 39. The lumber as received from the mill, and which has usually been subjected to the process of air seasoning, commonly has a hard surface which serves to prevent the ready escape of moisture from the interior thereof. For softening or removing this hard surface, the lumber, while in the portion X of thecompartment, is subjected to the action of hot and moist'steam permitted to escape .into said compartment through the spray heads of the group 37 and after being subjected to such steam for a suitable period the curtain 39 is drawn aside and the truck with its load of lumber is pushed along into that portion Y of the compartment just within the curtain 39, the latter being allowed to drop. A second truckwith freshA lumber may now be moved into portion X of the compartment and the steaming process repeated. The truck with its steamed lumber` standing in portion Y of the compartment is permitted to remain for a time while the lumber is subjected to the action of the dry and warm air flowing through the compartment and out through the cupola 41, such AWarm dry air serving to carry off surface moisture from the lumber which may have condensed thereon during the steaming process. The lumber will now be traversed intermittently by stages toward the discharge end of the compartment, fresh loads of steamed lumber being admitted from time to time so that the process may be substantially continuous. The air which is admitted through the intakes 30, 31, will rise through the first coil 32 whereby it will be very sub-` stantially raised in temperature. rl`his air as it rises will pass through that portion of the lumber which 4has nearly reached the discharge end of the compartment and after absorbingk a certain amount of moisture therefrom will move upwardly, in the com-v partment and then 'outwardly and downwardly through the openings 22 and -iiues 21. As the air passes downwardly through the refrigerating coils 42 whereby its temperature is lowered and a large portion of the moisture contained therein will be condensed and deposited. The air from the first set of flues 21 then moves through the passages 29, into .the ducts 25, 26, and if the first dampers 44, 45 in such ducts are closed all of such air will be discharged through the next succeedin openings 27, 281 The air lthus discharged w1ll pass upwardly through the next heating 'coil 32, through the truck load of lumber located directly above and thence to the next fiues 2l in order. The air is thus caused to pass successively over heating coils, through a stack of lumber, and thence over a cooling coil whereby its moisture is condensed, thence through a heating coil and so on from one end of the compartment to the other, being lfinally discharged through the cupola 41.

If for any reason it be desired to cause the air to pass directly from one portion of the compartment to the other the proper dampers 44 may be opened and at the same time the heating and cooling elements in that portion of the compartment which it is desired to cut out, may be shut olf, thus eliminatingr the tendency of the air to circulate through such portion of the compartment due to variations in temperature therein. If during the process it be found that the temperature is'so high as 'to cause a secondary case hardening effect moist steam may be emitted through the spray heads 38 whereby again to meisten the surface of the lumber.

As will be noted from the abovefdescription, air as it enters the compartment passes upwardly, thence laterally and downwardly,

thence inwardly moving longitudinally ofl two such helical paths in which the direc-`- tion of flow is reversed, the axes of suchhelical paths lying longitudinally of the compartment and in substantially horizontal planes.

The transverse arrangement of the independent heating coils of the groups 32, '33 permits of a rapid and accurate adjustment of the temperature at desired portions of the compartment and by the use of suitable instruments as indicated' at 43 (Fig. 5) the user of the device may determine from time to time the condition of the air at various locations in the compartment and thus by proper manipulation ofthe various control lng valves may maintain its temperature and moisture content at the proper point. It is to be understood that the exact arrangement of iues and passageways, or of the heating and cooling coils, or ofthe spray heads is not essential to the carrying out of the invention, as various modifications thereof mayl readily be y.substituted without departing from the spirit ofthe invention.

I claim: v

1. A dry kiln device comprising a cham-I ber, means for causing air to circulate therein in a substantially helical path, and cooling means interposed in=an individual coil of saidv path.

2. A device of the class described comprising a chamber, means 'for causing air to circulate therethrough in a substantially helical path and air drying means interposed in an individual coil of said'path.

3. In va device of the class described comprising a chamber, means for causing a flow of Aa1r 1n intersecting and substantially heliv cal paths therethrough, means'for heating such air, and means for imparting moisture thereto. Y

4. In combination in a device of the class described and having a longitudinally extending chamber, means lfor causing a flow .of air therethrough in a substantially helical path, means for heating such air and means for removing Lmoisture therefrom.

v5v. A dry kiln having a longitudinally eX- tending chamber, and meansfor causing air to movefin repeated cycles first Iupwardly at the' axial portion of said chamber, then outwardly in opposite directions, 'then downwardly, and then longitudinally of the chamber. y

6. A dry kiln having a longitudinally extending chamber, and means for causing airn to .flow lengthwise thereof in helical paths having substantially parallel axes.

7 A dry kiln having a longitudinally eX- tending chamber, and means for causing air to `flow lengthwisethereof in helical paths, the air in corresponding turns of adjacent helices moving in opposite directions. '8. A dry kiln having a longitudinally ex? tending chamber, and means for cau-sing air to circulate therethrough Iin helical paths having substantially parallel axes, correspondlng turns of said helices intersecting in the axial region of said chamber.

9. A dry kiln for lumber having, in-comy bination, means whereby lumber may be supported therein, and va series of 'trans-v versely arranged heating coils spaced longitudinally of said kiln and in a plane below said su porting means, said coils being of gradual y increasing heating capacity from one end of said kiln to the other.

10. In a kiln for drying lumber, in combination a track along which lumber may be traversed from one end of said kiln to the other, a series of heating coils arranged transversely of said track and below the same, said coils being spaced longitudinally of the kiln, and means for admitting heating iluid to said coils, the capacity of said coi s gradually increasing from the receiving end of the kiln to the delivery end thereof.

11. In a dry kiln, means for causing air to circulate therethrough in a substantially helical path, and means for permitting the air to move longitudinally past one or more coils of said helix. Y

12. In a dry kiln, means for causing air to circulate therethrough in a substantially helical path, said means comprising restricted passages and open chambers in alternation and means permitting the movement of air longitudinally past certain of said passages and chambers.

13. In a dry kiln, means for causing air to circulate longitudinally thereof in a substantially helical path, said means including restricted passages and open chambers in alter'- nation, and damper controlled by-passes associated with certain of said passages whereby to permit the movement 'of air longitudinally ast certain of said chambers.

14. In a. dry iln for lumber, a chamber, a series of transversely extending and independent heating coils located at spaced intervals longitudinally of said chamber, a series of cooling coils, a plurality of steam jets, and means for controlling the operation of said coils and of said steam jets.

15. In an apparatus of the class described and having a longitudinally extending chamber, a series of spaced air inlet ducts opening into said chamber at points located between the walls of said chamber, and a series of air outlet iues opening through the walls of said chamber, said latter openings being located opposite the intervals between the respective inlet openings.

16. In a device for drying lumber, means providing a longitudinal chamber having ottom and side walls, means for admitting air at separated points adjacent the longitudinal center of the bottom wall, and means providing for the discharge of air at separated points adjacent the upper portion of a side wall, said latter points being located respectively opposite the intervals between said first named points.

17. In combination in a structure having a bottom wall and side walls constituting a longitudinal chamber, a plurality of air inletducts opening at spaced intervals into said chamber adjacent the longitudinal center of the bottom wall thereof, means providing a plurality of air outlet lues opening adjacent the top of one of said side walls, said inlet and outlet openings being spaced in alternating relation longitudinally of the chamber, and means above certain of said inlet openings for heating air entering thereat.

18. In combination in a dry kiln having a longitudinally extending chamber having bottom and side walls, a plurality of series of air ducts having inlet openings spaced longitudinally of said chamber and adjacent the longitudinal center 0f the bottom wall thereof, and a series of-air discharge flues opening at spaced distances at the upper portion of each of said side walls, the openings of the inlet ducts and discharge fines alternating longitudinally of the chamber.

19. In a dry kiln, having a longitudinally extending chamber, a series of inlet ducts having spaced openings, a series of discharge flues having openings alternating with said inlet openings, and means for connecting a discharge flue with an adjacent inlet duct.

20. In a dry kiln having a chamber for the reception of material to be dried, a series of air inlet ducts opening at spaced intervals into said chamber, a series of outlet flues opening at spaced intervals from said chamber, and means connecting an outlet iue with the next successive inlet duct in a given direction.

21. In combination in an apparatus for ends, a series of air inlet ducts having openings spaced longitudinally of said chamber, a series of outlet fines having openings spaced in alternation with said inlet openings, means connecting each outlet flue with the next succeeding inlet duct in a direction from the discharging end toward the receiving end of said chamber, and means Jfor heating air located between the respective inlet openings and the next successive outlet opening.

22. In combination in a dry kiln having a receiving and discharging opening, a series of air inlet ducts having openings spaced longitudinally of said chamber, a series of outlet lues having openings spaced in alternation with said inlet openings, means connecting the respective outlet fluesy with the next succeeding inlet duct in the order of progression from the discharge opening of said kiln toward the receiving opening, and means associated with said connecting means for cooling the air passing therethrough.

Signed by me at Boston, Massachusetts, this 17th day of September, 1920.

ROBERT W. KENT. 

